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Displacement reactions

A displacement reaction is one in which a more reactive element replaces a less reactive element from one of its compounds. We commonly see this in the reactivity series for metals. For example magnesium metal will displace the less reactive zinc metal from zinc sulfate solution:

You might like to look at the spectacular Thermit reaction which can be found here. This is an example of a displacement reaction in which the more reactive aluminium metal displaces molten iron from iron(III) oxide powder.

Displacement reactions also occur with the halogens. Fluorine is the most reactive of all the halogens and will displace all of them from their compounds. It is too dangerous to use in a school/college laboratory as many substances burst into flames or explode in contact with fluorine. The following example shows it displacing chlorine from sodium chloride:

You should have met at the start of the course the principle of a spectator ion. In the above example nothing has happened to the sodium ion so it is often left out of the equation to give an ionic equation. These are, perhaps, better as they only show the changes which occur during the reaction: